Conventionally, there has been known a particulate measurement system which measures the amount of particulates (e.g., soot) contained in a gas under measurement (for example, exhaust gas discharged from an internal combustion engine or the like) (see, for example, Japanese Patent Application Laid-Open (kokai) No. 2013-195069).
Such a particulate measurement system includes a particulate sensor which is exposed to the gas under measurement and detects particulates. The particulate sensor includes an ion generation section, an electrification chamber, and a trapping section. Also, in use, the particulate sensor is connected to a sensor drive section for driving the particulate sensor.
Through use of ions generated at the ion generation section by means of corona discharge, the particulate measurement system causes the ions to adhere to at least a portion of particulates contained in the gas under measurement in the electrification chamber to produce electrified particulates. The particulate measurement system measures the amount of particulates on the basis of the amount of the electrified particulates (in other words, the amount of ions trapped by the trapping section). Specifically, a particulate computation section provided in the sensor drive section (in a sensor control section) detects a signal current which flows between a primary-side reference potential representing the reference potential of a primary coil of an isolation transformer for corona discharge and a secondary-side reference potential representing the reference potential of a secondary coil of the isolation transformer for corona discharge, the signal current flowing in accordance with the amount of the electrified particulates, and computes (measures) the amount of particulates by using this signal current.